Systems for accessing a central pulmonary artery

ABSTRACT

A system for accessing a central pulmonary artery includes an elongate, flexible tubular catheter, having a proximal end, a distal end and a catheter hub on the proximal end. An elongate, flexible rail has a proximal end, a distal end and a rail hub on the proximal end. The rail has a distal advance segment which extends at least about 10 cm beyond the distal end of the catheter when the catheter hub is adjacent the rail hub.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority benefit under 35 U.S.C. § 119(e) ofU.S. Provisional Patent Application No. 62/950,058, filed Dec. 18, 2019and U.S. Provisional Patent Application No. 63/064,273, filed Aug. 11,2020, the entirety of each of which is hereby incorporated by referenceherein.

BACKGROUND OF THE INVENTION

Thrombotic restrictions and occlusions within a patient's blood vesselsare a significant medical problem and often require intervention toremove these restrictions and blockages to restore health to patients.While applicable to a wide range of vascular applications, the followingbackground illuminates the problems through the example of patientssuffering with Pulmonary Embolisms.

Venous thromboembolic disease (VTE) is a worldwide crisis. There areover 10 million cases of deep vein thrombosis (DVT) and pulmonaryembolism (PE) diagnosed globally per year, with 1 million casesoccurring in the United States and over 700,000 in France, Italy,Germany, Spain, Sweden, and the United Kingdom combined each year. Thereare approximately 60,000 to 100,000 deaths from PE in the United Stateseach year. DVT and PE are part of the same continuum of disease, withover 95% of emboli originating in the lower extremities. When PE occurs,the severity depends on the embolic burden and its effect on the rightventricle as well as underlying cardiopulmonary comorbidities. Death canresult from the acute increase in pulmonary artery (PA) pressure withincreased right ventricular (RV) afterload and dysfunction.

Patients with high-risk pulmonary embolism (PE) were treated primarilywith thrombolytic therapy delivered systemically or more locally throughCatheter Directed Thrombolytics. These approaches result in multiplecatheterization lab visits, lengthy hospital stays and often lead tobleeding complications. Newer approaches to PE treatment include singlesession thrombectomy treatments without the use of thrombolytics. Thesethrombectomy treatments include delivering a catheter into the PA toremove the thrombus through aspiration, and secondary tools may alsomacerate or disrupt the thrombus prior to aspiration. While thrombectomyresults in fewer bleeding complications and reduced hospital stayscompared to thrombolytics, there is much to be improved upon given thechallenges of the procedure itself, including the ability to capture abroad spectrum of thrombus types and reduce the total volume of bloodloss during the procedure.

The thrombectomy catheter is introduced through an introducer puncturein a large diameter vein. A flexible guide wire is passed through theintroducer into the vein and the introducer is removed. The flexibleguidewire provides a rail for a flexible guide catheter to be advancedthrough the right atrium into the right ventricle and into the pulmonaryartery. The flexible guidewire is removed and replaced with a stiffguidewire. The large diameter thrombectomy catheter with support dilatoris then advanced over the stiff guidewire to the pulmonary artery andthe dilator is removed. If the large diameter thrombectomy catheter isnot successful in accessing or aspirating thrombus in a more distalportion of the vessel, a smaller diameter catheter may be insertedthrough the large diameter catheter. This procedure, with multipleaccessory devices and exchanges, is expensive, requires advancedcatheter skills, results in a high volume of blood loss, and may notresult in optimal patient outcomes.

SUMMARY

There is provided in accordance with one aspect of the invention, asystem for advancing a large bore catheter to a remote site, such as acentral pulmonary artery. The system comprises an elongate, flexibletubular catheter, having a proximal end, a distal end and a catheter hubon the proximal end, and an elongate, flexible rail, having a proximalend, a distal advance segment having a distal end and a rail hub on theproximal end. The distal end of the rail extends at least about 5 cm or10 cm or 15 cm or more beyond the distal end of the catheter when thecatheter hub is adjacent the rail hub.

The system may further comprise an engagement structure on the catheterhub, configured to releasably engage a complementary engagementstructure on the rail hub. The rail may increase in flexibility in adistal direction, and may include a guidewire lumen. The guidewire lumenmay be configured to accommodate a guidewire having a diameter of nogreater than about 0.035″ and the rail has an outside diameter of nogreater than about 0.025″ smaller than the inside diameter of theaspiration catheter. The catheter hub may comprise a hemostasis valve.

The wall thickness of the rail may be at least about 0.05 inches, or atleast about 0.10 inches. The rail may comprise a proximal segmentseparated from the distal advance segment by a transition. The distaladvance segment may have a greater flexibility than the proximalsegment.

The access catheter may be at least about 8 French, or at least about 20French. The access catheter hub may comprise a projection configured tosnap fit into a complementary recess on the rail hub.

The system may further comprise a thrombus evacuation catheterconfigured to extend through the access catheter, and may comprise athrombus engagement tool configured to extend through the thrombusevacuation catheter. The thrombus engagement tool may comprise anelongate flexible body having a thrombus engagement tip with a helicalthread. The thread may extend from about two to about 10 revolutionsaround the elongate flexible body. The thread may have a maximumdiameter that is no more than about 60% of an inside diameter of anadjacent portion of the thrombus evacuation catheter. The thrombusengagement tool may further comprise a handle on the proximal end,configured to permit manual rotation of the thrombus engagement tool.

In accordance with another aspect of the invention there is provided amethod of advancing a catheter to a target vascular site. The methodcomprises the steps of providing a catheter having a guiding railextending therethrough, the catheter having a catheter distal end andthe rail having a rail distal end. With the rail distal end positionedat least about 10 cm distal to the catheter distal end, advancing therail distal end to the target vascular site; and thereafter advancingthe catheter along the guiding rail to the target vascular site. Theadvancing the rail step may be accomplished by advancing the rail over aguidewire. The advancing the rail step may be accomplished while therail distal end is at least about 10 cm distal to the catheter distalend. The method may further comprise the step of unlocking the catheterfrom the guiding rail prior to the advancing the catheter along theguiding rail step.

The advancing the rail distal end step may comprise advancing the raildistal end from the vena cava through the tricuspid and pulmonary valvesof the heart into the central pulmonary artery while the distal end ofthe catheter remains in the vena cava. The advancing the catheter stepmay comprise advancing the catheter distal end from the vena cavathrough the tricuspid and pulmonary valves of the heart into the centralpulmonary artery over the guiding rail, following locating the distalend of the rail in the central pulmonary artery.

The advancing the rail distal end step may comprise advancing the raildistal end from the vena cava through the tricuspid valve beforeadvancing the catheter along the rail.

The advancing the catheter step may be accomplished over a guidewire,and may be accomplished with a guidewire extending through a cannulationin the rail, or may be accomplished with a guidewire extending throughthe catheter. The catheter may be at least about 8 French, or at leastabout 24 French, and the rail may substantially fill (e.g., at leastabout 80% or 90% or more of the cross section of) the catheter lumen.

The advancing the rail distal end step may comprise advancing the raildistal end through at least one valve before advancing the catheteralong the rail and through the valve. The advancing the rail distal endstep may comprises advancing the rail distal end through a vascularobstruction before advancing the catheter along the rail and through theobstruction. The advancing the rail distal end step may compriseadvancing the rail distal end through a tissue aperture before advancingthe catheter along the rail and through the aperture.

The method may further comprise the step of removing the rail followingthe advancing the catheter step, and may further comprise the step ofadvancing a clot evacuation catheter through the lumen to the targetvascular site. The method may further comprise the step of applyingvacuum to the clot evacuation catheter, and may further comprise thestep of advancing a thrombus engagement tool through the clot evacuationcatheter. The thrombus engagement tool may be manually rotated to engagethe thrombus.

In accordance with a further aspect of the invention, there is provideda method of removing a clot from a pulmonary artery to treat a pulmonaryembolism. The method comprises the steps of providing a large borecatheter having a guiding rail extending therethrough, the large borecatheter having a large bore catheter distal end and the rail having arail distal end. With the rail distal end at least about 15 cm distal tothe large bore catheter distal end, the rail distal end is advanced fromthe vena cava through the tricuspid and pulmonary valves of the heartinto the central pulmonary artery while the distal end of the large borecatheter remains in the vena cava. The large bore catheter is thereafteradvanced distally over the rail until the large bore catheter distal endis at least as far as the central pulmonary artery. The rail isthereafter proximally removed from the large bore catheter, and at leasta portion of a clot is drawn from a pulmonary artery into the large borecatheter. The drawing step may be accomplished using vacuum.

The method may further comprise the step of advancing a clot capturecatheter through the large bore catheter following the proximallyremoving the rail step, and may further comprise the step of advancing aclot engagement tool through the clot capture catheter. The clotengagement tool may be manually rotated to engage the clot.

There is also provided a method of removing foreign material from thevascular system, comprising the steps of positioning the distal tip of asensing catheter in proximity to a target foreign material; propagatinga signal from the sensing catheter; receiving a return signal; andcapturing and removing at least a portion of the foreign material whenthe return signal is indicative of a foreign material located within acapture zone. The capturing and removing steps may be accomplished bythe sensing catheter. The method may further comprise removing thesensing catheter following the receiving a return signal step, andintroducing a clot capture catheter to accomplish the capturing andremoving steps.

The foreign material may be a clot, which may be in the venous system,such as a deep vein thrombosis or a pulmonary embolism.

The return signal may enable characterization of tissue within thecapture zone, and may enable differentiation between clot and vesselwall within the capture zone. The propagating a signal step may comprisepropagating an ultrasound signal or an electromagnetic signal such as inthe UV-visible range. The electromagnetic signal may comprise multiplewavelengths.

The propagating a signal step may comprise propagating visible lightthrough the sensing catheter and beyond the distal tip. The method mayfurther comprise receiving the return signal using a sensor carried bythe sensing catheter. A visible light pathway may be created throughblood between the distal tip and the target foreign material. The stepof creating a visible light pathway through blood between the distal tipand the target foreign material may comprise infusing an opticallytransparent medium to displace blood from the pathway. The method mayfurther comprise the step of deploying a barrier to temporarily containat least a portion of the optically transparent medium within thepathway. The barrier may be deployed from the sensing catheter or fromthe aspiration catheter.

The differentiation may be accomplished by a clinician, observing animage generated by the return signal. The differentiation may beaccomplished by a processor configured to differentiate between returnsignals indicative of either a foreign material or a vessel wall. Theprocessor may further be configured to generate an indicium in responseto the differentiation between a foreign material and a vessel wall. Theindicium may comprise an audio or visual signal. The sensing cathetermay be axially reciprocally introduced through an access catheter. Themethod may further comprise the step of proximally retracting thesensing catheter through the access catheter following the receiving areturn signal, and may further comprise the step of distally advancing aclot capture catheter through the access catheter and capturing andremoving at least a portion of the foreign material using the clotcapture catheter.

Any of the methods disclosed herein may further comprise the step ofdeflecting the tip laterally in response to detecting vessel wall withinthe capture zone, prior to the capturing and removing steps.

In accordance with a further aspect of the invention, there is provideda dual dilator access system, comprising a large diameter accesscatheter, having an elongate tubular body with a proximal end, a distalend and a central lumen extending axially therethrough. A small diametercatheter is axially movably slidable through the central lumen. A firstdilator is extendable through the central lumen, in between the smalldiameter catheter and the large diameter catheter; and a second dilatorextendable through the small diameter catheter. The large diametercatheter may be an aspiration catheter. The small diameter catheter maybe a clot grabber catheter.

The system may further comprise a proximal coupling for interlocking thelarge diameter catheter and the small diameter catheter. The firstdilator may have a tapered distal end. The large diameter accesscatheter may be at least about 14 French. The tapered distal end may bepositionable beyond the distal end of the small diameter catheter. Theclot grabber catheter may include a distal tip with a helical thread.The small diameter catheter may comprises an imaging catheter.

The first dilator may have a split line along which it can split forproximal retraction and removal. The split line may comprise a weakeningin the wall or an axial scoring line.

The large diameter access catheter may comprise an inside surfacedefining the central lumen, and the inside surface comprises at leastone surface discontinuity for influencing the behavior of material drawninto the central lumen. The surface discontinuity may comprise a ridge.A plurality of axially extending, circumferentially spaced apart ridgesmay be provided along at least a distal zone of the catheter. The distalzone may extend proximally from the distal end within the range of fromabout 1 to about 20 cm, and the discontinuity may extend all the way tothe proximal end of the catheter. The ridge may be in a spiralconfiguration. The surface discontinuity may comprise at least one rampand edge for permitting material to travel proximally in the centrallumen and resisting distal travel of the material in the lumen. Theremay be a plurality of ramps which incline radially inwardly in theproximal direction and each terminate in a proximal edge. The centrallumen may have a non circular transverse cross sectional configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic side elevational view of a thromboembolic imagingcatheter.

FIG. 1B is a distal end view of the catheter of FIG. 1A.

FIG. 1C illustrates the catheter of FIG. 1A, extending through a lumenin an aspiration catheter.

FIG. 2A is a schematic side elevational view of a thromboembolic thermalsensing catheter.

FIG. 2B is a distal end view of the catheter of FIG. 2A.

FIG. 3A is a schematic side elevational view of a thromboembolic forcesensing catheter.

FIG. 3B is a distal end view of the catheter of FIG. 3A.

FIG. 4A is a schematic side elevational view of a thromboembolicultrasound catheter.

FIG. 4B is a distal end view of the catheter of FIG. 4A.

FIG. 5A is a schematic side elevational view of a thromboembolicelectromagnetic spectrum imaging catheter.

FIG. 5B is a distal end view of the catheter of FIG. 5A.

FIG. 5C is a distal end view of a variation of the catheter of FIG. 5A.

FIG. 6 is a side elevational view of the components in a thromboembolicvisualization and aspiration system.

FIG. 7A is a side elevational view of a catheter having an internal stopring.

FIG. 7B is a longitudinal cross section through the catheter of FIG. 8A,and detail view of the stop ring.

FIG. 7C is a side elevational view of a thrombus engagement tool havinga complementary limit for engaging the stop ring of FIGS. 7A and 7B.

FIG. 7D is a side elevational view of a distal portion of the thrombusengagement tool of FIG. 7C.

FIG. 7E is a longitudinal cross section through the thrombus engagementtool of FIG. 7D.

FIG. 7F is a perspective cut away view of a distal portion of thethrombus engagement tool of FIG. 7C.

FIG. 7G is a transverse cross section through a distal stopper carriedby the thrombus engagement tool.

FIG. 7H is a transverse cross section through an alternative distalstopper.

FIGS. 8A-8C are side elevational and cross sectional views of tipprofiles, showing proximal and distal tapers of the helical threadenvelope.

FIG. 9 is an end elevational view of a helical tip havingcircumferentially varying major diameter creating a radially non-uniformseparation from the catheter lumen wall.

FIG. 10 is an end perspective view of a cannulated helical tip elementwith a lumen for a guidewire or other devices or infusion or aspirationof fluids.

FIG. 11 is a schematic side elevational view of an over the wire helicaltipped structure.

FIG. 12 is a schematic side elevational view of a helical tippedstructure with a fixed guide wire tip.

FIG. 13 is a side elevational view of a large bore catheter.

FIG. 14 is a side elevational partial cross section of the catheter ofFIG. 13, having a cannulated guide rail extending therethrough over aguidewire.

FIG. 15 is a cross sectional view through a dual dilator system such asthat shown in FIG. 16.

FIG. 16 is a side elevational cross section of a distal portion of adual dilator system of the present invention.

FIG. 17 is a cross section as in FIG. 16, with a distal tip formed bythe tubular dilator.

FIG. 18 is a side elevational view of a portion of a tubular dilatorhaving a separation line to allow longitudinal splitting of the sidewallduring proximal retraction from the system.

FIG. 19A is a longitudinal cross-sectional view through a distal zone ofa catheter, having axially extending surface structures on the insidesurface of the catheter wall.

FIG. 19B is a longitudinal cross-sectional view as in FIG. 19A, havinghelical surface structures on the inside surface of the catheter wall.

FIG. 20 illustrates transverse cross-sectional views through thecatheter of FIG. 19A, showing different ridge and groove configurations.

FIG. 21 illustrates an inside surface of a catheter wall havingdifferential friction surface structures for facilitating proximalmovement of thrombus and inhibiting distal movement of thrombus.

FIG. 22 shows an angled distal catheter tip.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The devices and systems of the present invention include catheter-basedtechnology that enables accessing and retrieving a vascular obstruction.In some implementations of the system, a separate facilitator maybeprovided for advancing through an aspiration catheter to facilitateengagement of the obstruction. In other implementations of the system,sensors are provided which provide the clinician with information aboutthe presence, amount, and characteristics of tissue in front of thecatheter. This enables valuable diagnostic information such as theidentity of tissue within a clot capture zone adjacent and beyond thedistal tip of the catheter, e.g., whether the catheter is aimed at clotor at the vessel wall, and potentially assists in developing anappropriate treatment strategy. As used herein, terms like clot,thrombus, embolization, foreign matter and the like will be consideredsynonymous unless otherwise described.

For instance, when planning to remove a pulmonary embolism from apulmonary artery, it may be valuable to differentiate thrombus fromvascular tissue and confirm 1) the presence and location of thethrombus, 2) the size and shape of the thrombus, and 3) the morphologyand composition of the thrombus. All of these can be accomplishedutilizing the single, low profile catheter in accordance with thepresent invention. The present sensing catheter described in furtherdetail below includes, but is not limited to one or more sensors of thefollowing modalities: CMOS imaging (or CCD) to enable visualization;thermal sensing; force sensing; ultrasound imaging; infrared imaging;spectroscopy tomography; or electrochemical sensing.

The sensing catheter is thus enabled to provide clinical data of thefollowing types: Location of target obstruction; thrombus versus tissuewall; size and shape; mechanical properties like hardness/stiffness;temperature differences; or morphology/age.

Although primarily described in the context of a pulmonary arteryembolectomy catheter with a target tissue characterization feature,catheters of the present invention can readily be adapted for use inremoval of deep vein thrombosis or other vascular (e.g., neurovascular,other peripheral vascular, coronary), emboli or obstructions as will beunderstood in the art. Any of the devices disclosed herein can also bemodified to incorporate additional structures, such as clot grabbing andretrieval features, partial length or full length guidewire lumen forover the wire or rapid exchange guidance, permanent or removable columnstrength enhancing mandrels, two or more lumens such as to permit drug,contrast or irrigant or optical field clearing infusion or to supplyinflation media to an inflatable balloon carried by the catheter.

Any of the catheters disclosed herein may have a deflectable orpreshaped curved or angled distal steering zone. At least one andoptionally two or three or more pull wires may axially extend throughcorresponding pull wire lumen(s), to enable lateral deflection of thedistal tip of the catheter. A single pull wire can provide deflection ina single direction and plane, to cooperate with rotation of the catheterto achieve 360 degree manuverability. Two or three or more pull wires,typically spaced equidistantly around the circumference of the catheterbody, enable greater steerability without the need for catheterrotation. Deflection or preshaped curvature or angulation of the distaltip enables redirection of the tissue capture zone away from a firsttarget tissue (e.g., healthy vessel wall) to a second target tissue(e.g., a clot). Catheters of the present invention can include anycombination of the foregoing features, depending upon the intendedclinical application and desired functionality as will be readilyapparent to one of skill in the art in view of the disclosure herein.

In addition, the present invention will be described primarily in thecontext of removing obstructive material from the pulmonary artery butmay have applicability for use throughout the body wherever it may bedesirable to characterize a target tissue to support a clinical decisionto remove or treat a first target tissue or redirect the catheter to adifferent, second target tissue. For example, sensing catheter shafts inaccordance with the present invention may be dimensioned for usethroughout the coronary, peripheral, and neurovasculature, both arterialand venous, the gastrointestinal tract, the urethra, ureters, Fallopiantubes and other lumens and potential lumens, as well. The sensingcatheter of the present invention may also be used to provide minimallyinvasive percutaneous tissue access, such as for diagnostic ortherapeutic access to a solid tissue target (e.g., breast or liver orbrain biopsy or tissue excision), access to bones such as the spine forsurface characterization and other applications.

Referring to FIGS. 1A and 1B, a sensing catheter generally comprises anelongated flexible tubular body 10 extending between a proximal end 12and a distal functional end 14. The length of the tubular body dependsupon the desired application. For example, catheter lengths from about120 cm to about 150 cm or more are typical for use in femoral accesspercutaneous transluminal coronary applications. Intracranial or otherapplications may call for a different catheter shaft length dependingupon the vascular access site, as will be understood in the art.

In certain embodiments intended to treat pulmonary embolism via afemoral vein access site, the catheter 10 will generally have an axiallength within the range of from about 80 cm to about 110 cm for aprimary treatment catheter and from about 130 cm to about 150 cm for asecondary catheter intended to advance through a primary catheter.Outside diameters may be within the range of from about 8 F to about 32F depending upon the procedure and intended clinical performance.

The distal end 14 of catheter 10 is provided with at least one sensor 16for characterizing the clot, vessel wall, or other target tissue. In anembodiment intended for optical visualization, an optical sensor such asa CMOS or CCD chip may be located at the distal end of the catheter, orin a proximal handpiece or module, and optically coupled to a fiberoptic element extending axially throughout the length of the catheter. Alight source such as an LED is also provided, either at the distal endof the catheter, or at the proximal end of the catheter and opticallycoupled to a fiber optic light guide extending through the catheterbody.

The catheter 10 may additionally be provided with a guide wire lumen 17extending between a guide wire port on the distal end 14 of the catheter10 and a proximal guide wire port. The proximal guide wire port may bethrough a sidewall of the catheter 10 in a rapid exchangeimplementation, or may be provided on the hub 27 in an over the wireconfiguration. One or two or more additional ports or electricalconnectors may be provided on the proximal hub 27, depending upon thefunctionality of the catheter.

The catheter is provided with at least one infusion lumen 18, and two inthe illustrated embodiment, extending from a proximal infusion port 22on a proximal hub 27 to a corresponding exit port on the distal end 14of the catheter. A deflection mechanism may be provided, for laterallydeflecting a distal steering zone on the catheter 10. In oneimplementation, a pull wire lumen 19 extends from a proximal deflectioncontrol (not illustrated) carried by the hub 27 and extending distallyto the deflection mechanism. The proximal control may comprise arotatable control such as a ring that may be rotatable about thelongitudinal axis of the catheter, or a rotatable knob, a slider switch,or other suitable control for placing a control wire under tension orcompression. The deflection mechanism may form a deflection zone on adistal portion of the catheter 10, in which an axial length of thecatheter sidewall is provided on a first side with a plurality oftransverse slots, leaving an opposing spine side with relatively highercolumn strength. The deflection wire may be attached to the side walldistally of the slots. Proximal retraction of the deflection wire causesaxial compression of the slotted side of the tubular body therebydeflecting the axis away from the spine side and towards the slottedside of the tubular body.

In use, a fluid media, optically transparent in the visible range (e.g.,water or saline) is infused from a source 33 and through lumen 18 todisplace blood in a visualization and capture zone 21 in front of thecatheter and create an optical path between the sensor and targettissue. A temporary barrier such as a hood 20 may be desirable tolengthen the dwell time of the optically transmissive media within theoptical path, before it is replaced with blood and become opticallyopaque in the visual range.

In the illustrated embodiment, the barrier is in the form of an imaginghood 20 such as a self expandable cone, to protect the viewing area fromblood flow. The barrier is carried by the distal end of the sensingcatheter and may be self expanding upon release from a restraint such asthe outer access catheter which may also be an aspiration catheter.

Alternatively, referring to FIG. 1C, the imaging hood 20 or otherbarrier may be carried by the aspiration catheter 26. In thisimplementation, the sensing catheter 10 may be advanced distally througha lumen 24 in the aspiration catheter 22, and the imaging hood 20utilized as described to facilitate establishment of an optical pathbetween the sensor and target tissue. The ID of the lumen 24 may be atleast about 0.005″ and in some implementations at least about 0.010″ or0.015″ or more greater than the OD of the imaging catheter 10 to providean aspiration lumen while the imaging catheter 10 is in place, and alsoaccommodate a guidewire 28.

Following confirmation by the sensing catheter 10 that the aspirationcatheter 26 is positioned at the desired site, the sensing catheter 10may be proximally retracted and the central lumen 24 can be used fordirect aspiration or to receive a clot capture catheter (discussedbelow) therethrough. At this point, the imaging hood 20 can perform theadditional and distinct function of helping advance the clot proximallyinto the aspiration catheter.

Image data from the image sensor is carried proximally through thecatheter by one or more conductors, to a connector 30, and via cable 32into a processor 25 for converting into a visual image or other visualand/or audible indicium of characterization of the target tissue. Theimage can be displayed on a conventional display such as a laptop,tablet, wall hung display or wearable display.

As an alternative to direct visualization in the visible light range, avariety of other characterizing modalities may be used to characterizetarget tissue. For example, referring to FIGS. 2A-2B, in a givenenvironment, the foreign material and healthy wall may have differentsurface temperatures. In this situation, a thermal sensing catheter 34may be provided with one or two or more distal temperature sensors 36.Intravascular thermal sensors are described, for example, in U.S. Pat.No. 9,420,955 entitled “Intravascular temperature Monitoring System andMethod”, the disclosure of which is hereby incorporated by reference inits entirety herein.

Alternatively, hemoglobin reflectivity measurement and optionalsimultaneous optical coherence tomography imaging capabilities may beadded to the catheter, as described in US published patent applicationNo. 2011/0077528 to Kemp et al, entitled Method and Apparatus forSimultaneous Hemoglobin Reflectivity Measurement and OCT Measurement,Thrombus Detection and Treatment, and OCT Flushing, published Mar. 31,2011, which is hereby incorporated in its entirety herein by reference.Hemoglobin reflectivity measurement enables differentiation between‘red’ thrombus and ‘white’ thrombus, which differ largely in theconcentration of red blood cells.

Alternatively, a chemistry-based sensor may be used which uses thechemical composition of the tissue to create a signal which candifferentiate between the foreign body and non-target tissue, orcharacterize different tissue types. For example, Fibrinogen has beenreported to have been detected using an electrochemical impedancebiosensor (EIB) formed by draping an erythrocyte membrane (EM)configured for the detection of fibrinogen. Measurements with the FIBmay reveal that the specific (selective) adsorption of fibrinogen ontothe EM causes a clear rise in the value of interfacial charge transferresistance. The sensing ability of the EIB for fibrinogen detection mayshow a wide linear range from 0.0001 to 5 mg/mL, with a limit ofdetection of 49 ng/mL (144 pM).

Preferably the sensors in general detect a relatively high level ofhemoglobin, or fibrinogen, or prothrombin, or other clotting pathwayfactors which would not be as abundant in vascular wall tissues.

The clot and native vessel wall may also vary in physical propertiessuch as compressibility or hardness. Referring to FIGS. 3A-3B, this maybe measured by one or two or more force, pressure, or displacementsensors 28 carried by the distal end 14 of a force sensing catheter 40.

In certain embodiments it may be desirable to interrogate tissue withinthe capture zone with a first signal, and then capture reflected orrebounded signal for comparison to characterize the target tissue. Forexample, referring to FIGS. 4A-4B, unitrasound catheter 44 may beprovided with ultrasound transmitter and receiver chips 46 which may becarried by the catheter 44 to interrogate tissue in the capture zone.

Depending upon the nature of the target tissue and adjacent healthytissue, any of a variety of other signals in the electromagneticspectrum may be propagated from an EMS imaging catheter 50 withreflected signal captured by the catheter to identify and define matterin front of catheter. See, e.g. FIGS. 5A-5C.

EMS imaging catheter 50 may comprise one or two or more transmitters 52for transmitting EMS imaging signals to target tissue and one or two ormore receivers 53 for sensing reflected EMS signals. Aspiration lumen 54may be provided, if aspiration is desired. One or more working channelsor delivery channels 56 may be provided, depending upon the desiredfunctionality.

The number and orientation of lumen, electrical conductors and otherstructures within the catheter body can be varied widely depending uponthe desired functionality of the catheter. For example, FIG. 5Cillustrates an alternate configuration for the catheter of FIG. 5 A, inwhich a guide wire lumen 17 has been provided along with a pull wirelumen 19 in a steerable implementation. An EMS sensor or sensor/receiverarray 58 may be provided, along with one or two fluid lumen 18 such asfor the delivery of saline and/or drug delivery and/or aspiration.

Intravascular sensing systems that may be adapted into the catheters ofthe present invention for characterizing material within the capturezone 21 as native vascular wall or foreign material are disclosed, forexample, in U.S. Pat. No. 10,534,129, issued Jan. 14, 2020 and entitled“System and method providing intracoronary laser speckle imaging for thedetection of vulnerable plaque”; U.S. Pat. No. 7,473,230, issued Jan. 6,2009 and entitled “Instrumented catheter with distance compensation tosense vulnerable plaque”; and U.S. Pat. No. 7,450,241, issued Nov. 11,2008 and entitles “Detecting vulnerable plaque”, the disclosures ofwhich are hereby incorporated in their entireties herein by reference.

In general, the distal end 14 of the sensing catheter 10 may be providedwith at least one signal transmitting surface and at least one signalreceiving surface. The transmitting surface is adapted to transmit asignal from the distal end of the catheter and generally in the distaldirection with respect to the longitudinal axis of the catheter. Thereceiving surface is adapted for receiving a reflected return signalwith at least a component of the signal traveling in a generallyproximal direction with respect to the distal end of the catheter. Inone embodiment, the transmitting surface comprises the distal end of afiber optic or fiber optic bundle, a distal light source, or atransparent window which may be a lens positioned at the distal end of afiber optic or fiber optic bundle or distal light source. Similarly, thereceiving surface may comprise a distal end of a receiving fiber opticor a distal sensor, a transparent window which may be a lens positioneddistally of the receiving fiber optic or sensor. In one embodiment, twotransmitting surfaces and two receiving surfaces may be provided eachcommunicating with a spectrometer via unique communication lines.

Electrical signals from the sensors may be transmitted to a spectrometeror other device suitable for the sensed signal, which remains outside ofthe patient. The construction and use of spectrometers such as tomeasure RGB and other UV, visible and IR wavelengths is well understoodin the pulse oximetry art, among others, and will not be disclosed indetail herein. In general, a transmitter/detector may be able totransmit multiple wavelengths of light, which propagate beyond thetransmit surface and into a target beyond the distal end of the sensingcatheter. Some of the transmitted light is absorbed in the target, whileother transmitted light is reflected back and received at the receivingsurface. The reflected light is thereafter propagated for processing.The optical absorption/reflection characteristics of the clot comparedto healthy vessel wall enable differentiation of the target tissuetypes.

Any of the foregoing sensing catheters may be utilized in theimage-guided PE or DVT thrombectomy system and procedure in accordancewith the present invention.

Referring to FIG. 6, the system for accessing and retrievingthrombo-emboli in accordance with the present invention generallycomprises an access catheter 40 such as a large bore (e.g. 24 Fr)catheter, an aspiration or evacuation catheter 62, optionally an imagingfunctionality, which may be a separate sensing catheter 64, and a clotretrieval tool 66 configured to be extendable through the evacuationcatheter 62.

One example of the method and use of the system is described below.

Femoral vein or internal jugular vein access is achieved usingconventional techniques.

An access catheter 60 such as a 24 Fr catheter is advanced through theright heart chambers and into the Pulmonary Artery.

Aspiration may be applied to the access catheter for clot removal in theproximal pulmonary artery. If that fails, a mechanical facilitatordevice such as clot retrieval tool 66 may be advanced through the accesscatheter 60 to assist with clot removal. If that fails, the evacuationcatheter 62 may be advanced through the 24 Fr access catheter 40 andadvanced to the thrombus.

If desired, the imaging catheter 64 may be advanced through theevacuation catheter 62 to identify and verify thrombus. Alternatively,when the imaging and evacuation catheters have been integrated, only onecatheter with both imaging elements and an evacuation lumen would needto be advanced through the 24 Fr access catheter 40 at this stage.

Aspiration is turned on to hold thrombus in place at the evacuationcollection funnel 20 while exchanging Imaging Catheter 64 for the clotretrieval catheter 62.

The thrombus engagement tool 66 may be advanced into the thrombus forthrombus engagement.

The thrombus engagement tool 66, evacuation catheter 62 and engagedthrombus are proximally retracted through the 24 Fr catheter 60.Retraction may be accomplished under optional aspiration to maintainattachment of the thrombus.

Optionally, the imaging catheter 64 may be reintroduced to confirmtarget thrombus removal and identify additional thrombus to remove.

Aspiration, exchange, engage, extract, re-image may be repeated asdesired.

Following aspiration, all catheters may be removed.

Additional details of the devices useful in the methods and systems ofthe present invention are discussed below.

Referring to FIGS. 7A and 7B, any of the aspiration catheters disclosedherein may be provided with an axial restraint for cooperating with acomplementary stopper on a thrombus engagement tool 2401 (FIG. 7C) topermit rotation of the thrombus engagement tool 2401 but limit thedistal axial range of travel of the thrombus engagement tool 2401.

The method of limiting distal advance of the core wire and helical tipelement may be achieved by a limit attached to the core wire or torquemember in sliding contact with an internal stop as described above, orin sliding contact with a stop surface carried on any of a variety ofaccessories or devices attached to the proximal end of the catheter inwhich the helical member assembly is contained. This includes aTuohey-Borst or other hemostasis valve accessory.

In the illustrated implementation, the restraint comprises at least oneprojection extending radially inwardly through the sidewall or from theinside surface of the tubular body, configured to restrict the insidediameter of the aspiration lumen and engage a distal face carried by thethrombus engagement tool. The restraint may comprise one or two or threeor four or more projections such as tabs, or, as illustrated, maycomprise an annular ring providing a continuous annular proximallyfacing restraint surface. In the illustrated implementation, therestraint is positioned in a distal location in the catheter e.g.,within about 20 cm or 10 cm or less from the distal end. This allowsprecise positioning of the distal thrombus engagement tool tip withrespect to the distal end of the catheter, decoupled from bending of thecatheter shaft, and prevent the distal tip from extending beyond apreset position such as the distal end of the catheter.

In other implementations, the restraint may be located at the proximalend of the catheter such as at the proximal hub, or even external to thecatheter, such as on the proximal end of the hub. For example, thethrombus engagement tool 66 may be provided with a handle 70 asillustrated in FIG. 6. Handle 70 comprise an axially elongate body 72configured to be twirled about its longitudinal axis between two orthree fingers of a single hand. Surface friction enhancing structuressuch as a plurality of axially extending flats or ridges 74 may beprovided on an exterior surface of the body 72. Distal end 76 may beconfigured to rotatably slide against a proximal surface 78 on the hub27 for evacuation catheter 62.

In certain clinical applications, it may be desirable for the helicaltip to be able to advance beyond the tip of the surrounding catheter,thus an axial limit system may be omitted, or may be configured topermit the desired axial orientation. For example, distal extension ofthe distal end of the helical tip beyond the distal end of the cathetermay be limited to no more than about 5 mm or 3 mm or 1.5 mm or 1.0 mm orless.

The limit on distal advance of the helical tip may include a firstconfiguration in which distal advance is limited to a first positionproximate the distal end of the evacuation catheter to prevent injury tothe vascular wall. Upon a user initiated adjustment, the helical tip maybe advanced to a second position out of the distal end of the catheterfor inspection and cleaning purposes. This adjustment of the limitingmechanism may be locked out following cleaning or inspection, to limitdistal travel to the first position to prevent an undesired degree ofexposure of the helical tip element when the system is within thepatient's vasculature.

In the illustrated embodiment, the restraint may be a metal (e.g.,nitinol, stainless steel, aluminum, etc.) circular band or ring orprotrusion 2402 mounted on or built into a sidewall 2403 of the catheternear the proximal hub, on the proximal hub on the proximal end of thecatheter shaft or near the distal tip. The restriction element 2402extends into the ID of the catheter. Further, the restriction element2402 may be radiopaque for visibility under fluoroscopy. The restrictionelement 2402 carries a proximally facing surface 2405 for example anannular circumferential bearing surface that extends into the innerdiameter of the catheter to provide a sliding interface with a stoppersuch as distal stopper 2414 (FIG. 7C) on the rotating core assembly. Forexample, the stopper 2414 may be a radially outwardly extending featureon the rotating assembly which interfaces with the restriction element2402 of the catheter to permit rotation but limit the distal advancementand prevent distal tip displacement beyond a desired relationship withthe catheter distal tip.

In one implementation, in its relaxed form prior to securing within thecatheter lumen, the ring 2402 is a C-shaped or cylinder shaped with anaxially extending slit to form a split ring. The ring 2402 is compressedusing a fixture that collapses the ring to a closed circle shape,allowing it to slide inside the (e.g., 0.071″) catheter. When the ringis released from the fixture, the ring expands radially to the largestdiameter permitted by the inside diameter of the catheter. The radialforce of the ring engages the insider surface of the catheter andresists axial displacement under the intended use applied forces. Inanother implementation, the ring is a fully closed, continuous annularstructure (like a typical marker band) and its distal end is slightlyflared in a radially outwardly direction to create a locking edge. Thering is inserted into the catheter from the distal end. The flaredsection with the locking edge keeps the ring in place when axial forceis applied from the proximal side.

Referring to FIGS. 7D and 7F, distal segment 2407 of the rotatable corewire comprises a torque coil 2412 surrounding a core wire 2410. Theillustrated torque coil 2412 comprises an outer coil 2413 concentricallysurrounding an inner coil 2415 having windings in opposite directions.

Alternatively, for an over-the-wire embodiment (e.g., FIG. 11)alternative torqueable structures may be utilized, including a polymerictube with an embedded metallic wire braid intended to be entirelyinserted over and rotated around a central guidewire. Additionally, thegeometry of the lumen of the torqueing member may minimize the spacebetween the lumen inner diameter and the guidewire so as to minimizefluid or airflow and virtually eliminate blood flow out of the lumenunder biologically typical pressures or air leakage to significantlyreduce vacuum pressures when a vacuum pump is used to create a vacuumthrough the aspiration catheter (60) near the distal end of the elongatestructure.

Although the coil 2412 is shown in FIGS. 7D, 7E and 7F as having aconstant diameter, this leaves an internal entrapped space between thecoil and the core wire, as a result of the tapering core wire 2410. Whenthe area of the aspiration lumen between the coil and the inside wall ofthe corresponding catheter is optimally maximized, the diameter of thecoil 2412 can taper smaller in the distal direction to track the taperof the core wire. This may be accomplished by winding the coil onto thecore wire which functions as a tapered mandrel, or using othertechniques known in the art. In this execution, the OD of the core wiretapers smaller in the distal direction, while the area of the aspirationlumen tapers larger in the distal direction.

As illustrated further in FIGS. 7D and 7E, the torque coil 2412 extendsbetween a proximal end 2430 and a distal end 2432. The proximal end 430is secured to a tapered portion of the core wire 2410. As illustrated inFIG. 7E, the core wire 2410 tapers from a larger diameter in a proximalzone to a smaller diameter in a distal zone 2434 with a distaltransition 436 between the tapered section and the distal zone 2434which may have a substantially constant diameter throughout. The insidediameter of the inner coil 2415 is complementary to (approximately thesame as) the outside diameter at the proximal end 2430 of the core wire2410. The tapered section of the core wire 2410 extends proximally fromthe distal transition 436 to a proximal transition (not illustrated)proximal to which the core wire 2410 has a constant diameter.

The torque coil 2412 may additionally be provided with a proximalradiopaque marker and/or connector such as a solder joint 2438. In theillustrated implementation, the proximal connector 2438 is in the formof an annular silver solder band, surrounding the inner coil 2415 andabutting a proximal end of the outer coil 2413.

The axial length of the torque coil 2412 may be within the range of fromabout 10 mm to about 50 mm and in some embodiments within the range offrom about 20 mm to about 40 mm. The distal transition 2436 may bepositioned within the range of from about 5 mm to about 20 mm and insome implementations within the range of from about 8 mm to about 12 mmfrom the proximal end of the distal cap 2420.

Referring to FIGS. 7E and 7F, the distal stopper 2414 may be providedwith one or two or three or more spokes 440, extending radiallyoutwardly from the outer coil 2413, and optionally supported by anannular hub 442 carried by the torque coil 2412. The spoke 440 maysupport a slider 441 having a peripheral surface 443, configured for asliding fit within the inside diameter of the delivery catheter lumen.Preferably at least three or four or five or more spokes 440 areprovided, circumferentially spaced apart equidistantly to providerotational balance. In the illustrated embodiment, three spokes 440 areprovided, spaced at approximately 120° intervals around thecircumference of the torque coil 2412.

The distal stopper 2414 carries a plurality of distal surfaces 446, suchas on the slider 441. The distal surface 446 is configured to slidablyengage a proximal surface of a stop on the inside diameter of thedelivery catheter, such as a proximally facing surface 2405 on aradially inwardly extending annular flange or ring 2402. See FIG. 7Bdiscussed previously. This creates an interference fit with a bearingsurface so that the distal stopper 2414 can rotate within the deliverycatheter, and travel in an axial distal direction no farther than whendistal surface 446 slideably engages the proximal surface 2405 on thestop ring 2402.

Referring to FIG. 7E, the distal end 432 of the torque coil 2412 isprovided with a distal cap 2420. Distal cap 2420 may comprise an annularband such as a radiopaque marker band, bonded to the outside surface ofthe inner coil 2415, and axially distally adjacent or overlapping adistal end of the outer coil 2413. A proximally extending attachmentsuch as an annular flange 2417 may be provided on the thrombusengagement tool tip 2416, for bonding to the distal cap 2420 and in theillustrated embodiment to the outer coil 2413. The distal cap 2420 mayalso be directly or indirectly bonded to a distal end of the core wire2410.

The thrombus engagement tool tip 2416 is provided with a distal end 450,and a clot engagement element such as a plurality of proximally and/orradially facing engagement surfaces. In the illustrated implementation,the clot engagement element comprises a helical flange 452 thatincreases in diameter in the proximal direction. The flange may extendat least about one full revolution and generally less than about five orfour or three revolutions about an extension of the longitudinal axis ofthe core wire 2410. The helical flange may be provided with a rounded,blunt edge 454, configured for slidably rotating within the tubulardelivery catheter. Additional tip configurations are discussed inconnection with FIGS. 8 and 9, below.

The maximum OD for the tip 2416 is generally at least about 0.005 inchesand preferably at least about 0.01 inches or 0.015 inches or moresmaller than the ID of the catheter aspiration lumen through which theembolism treatment system 2401 is intended to advance, measured at theaxial operating location of the tip 2416 when the stopper 2414 isengaged with the stop ring. For example, a tip having a maximum OD inthe range of from about 0.050-0.056 inches will be positioned within acatheter having a distal ID within the range of from about 0.068 toabout 0.073 inches, and in one embodiment about 0.071 inches. With thetip centered in the lumen of the delivery (aspiration) catheter, the tipis spaced from the inside wall of the catheter by a distance in alldirections of at least about 0.005 inches and in some embodiments atleast about 0.007 inches or 0.010 inches or more.

Thus an unimpeded flow path is created in the annular (if centered)space between the maximum OD of the tip, and the ID of the catheterlumen. This annular flow path cooperates with the vacuum and helical tipto grab and pull obstructive material into the catheter under rotationand vacuum. The annular flow path is significantly greater than any flowpath created by manufacturing tolerances in a tip configured to shearembolic material between the tip and the catheter wall.

Additional aspiration volume is obtained as a result of the helicalchannel defined between each two adjacent threads of the tip. A crosssectional area of the helical flow path of a tip having a maximum OD inthe range of from about 0.050 to about 0.056 inches will generally be atleast about 0.0003 square inches, and in some embodiments at least about0.00035 or at least about 0.000375 inches. The total aspiration flowpath across the helical tip is therefore the sum of the helical flowpath through the tip and the annular flow path defined between the OD ofthe tip and the ID of the catheter lumen.

The combination of a rounded edge 454 on the thread 452 and spacebetween the thread 452 and catheter inside wall enables aspiration boththrough the helical channel formed between adjacent helical threads aswell as around the outside of the tip 2416 such that the assembly isconfigured for engaging and capturing embolic material but not shearingit between a sharp edge and the inside wall of the catheter. The axiallength of the tip 2416 including the attachment sleeve 2417 is generallyless than about 6 mm, and preferably less than about 4 mm or 3 mm or 2.5mm or less depending upon desired performance.

The pitch of the thread 452 may vary generally within the range of fromabout 25 degrees to about 80 degrees, depending upon desiredperformance. Thread pitches within the range of from about 40-50 degreesmay work best for hard clots, while pitches within the range of fromabout 50 to 70 degrees may work best for soft clots. For someimplementations the pitch will be within the range of from about 40-65degrees or about 40-50 degrees.

The tip 2416 may additionally be provided with a feature for attractingand/or enhancing adhesion of the clot to the tip. For example, a texturesuch as a microporous, microparticulate, nanoporous or nanoparticulatesurface may be provided on the tip, either by treating the material ofthe tip or applying a coating. A coating of a clot attracting moietysuch as a polymer or drug may be applied to the surface of the tip. Forexample, a roughened Polyurathane (Tecothane, Tecoflex) coating may beapplied to the surface of at least the threads and optionally to theentire tip. The polyurethane may desirably be roughened such as by asolvent treatment after coating, and adhesion of the coating to the tipmay be enhanced by roughening the surface of the tip prior to coating.The entire tip may comprise a homogeneous construct of any of thematerials described above, or other polymeric materials, rather thanjust the coating.

Alternatively, the core wire 2410 may be provided with an insulatingcoating to allow propagation of a negative electric charge to bedelivered to the tip to attract thrombus. Two conductors may extendthroughout the length of the body, such as in a coaxial configuration,or a single conductor and an external grounding electrode may be used.Energy parameters and considerations are disclosed in U.S. Pat. No.10,028,782 to Orion and US patent publication No. 2018/0116717 to Taffet al., the disclosures of each of which are hereby expresslyincorporated by reference in their entireties herein. As a furtheralternative, the tip 2416 can be cooled to cryogenic temperatures toproduce a small frozen adhesion between the tip and the thrombus.Considerations for forming small cryogenic tips for intravascularcatheters are disclosed in US patent publication Nos. 2015/0112195 toBerger et al., and 2018/0116704 to Ryba et al., the disclosures of eachof which are hereby expressly incorporated by reference in theirentireties herein.

Referring to FIG. 7G, there is illustrated a cross section through adistal stopper 2414 in which the slider 441 is a continuouscircumferential wall having a continuous peripheral bearing surface 442.Three struts 440 are spaced apart to define three flow passageways 443extending axially therethrough. The sum of the surface areas of theleading edges of the struts 440 is preferably minimized as a percentageof the sum of the surface areas of the open flow passageways 443. Thisallows maximum area for aspiration while still providing adequatesupport axially for the distal surface 446 (see FIG. 7F) to engage thecomplementary stop surface on the inside wall of the catheter andprevent the tip 2416 from advancing distally beyond a presetrelationship with the catheter. The sum of the leading (distal facing)surface area of the struts is generally less than about 45% andtypically is less than about 30% or 25% or 20% of the sum of the areasof the flow passageways 443.

In an embodiment having a torque coil 2412 with an OD of about 0.028inches, the OD of the stopper 2414 is about 0.068 inches. The wallthickness of the struts is generally less than about 0.015 inches andtypically less than about 0.010 inches and in some implementations lessthan about 0.008 inches or 0.005 inches or less. The struts 440 have alength in the catheter axial direction that is sufficient to support theassembly against distal travel beyond the catheter stop ring, and may beat least about 50% of the OD of the stopper 2414. In a stopper 2414having an OD of about 0.68 inches, the struts 2440 have an axial lengthof at least about 0.75 mm or 0.95 mm.

Referring to FIG. 7H, there is illustrated a stopper 2414 having threedistinct sliders 441 each supported by a unique strut 440. The sum ofthe circumference of the three peripheral surfaces is preferably no morethan about 75% and in some implementations no more than about 50% or 40%of the full circumference of a continuous circumferential peripheralsurface 442 as in FIG. 7G. This further increases the cross sectionalarea of the flow paths 443. In a catheter having an ID of no more thanabout 0.07 inches, an OD of the hub 443 of at least about 0.026 or 0.028or 0.030 or more, the sum of the flow paths 443 is at least about 0.0015inches, and preferably at least about 0.020 or 0.022 inches or more. Thearea of the leading edges of the struts 440 and sliders 441 ispreferably less than about 0.003 inches, and preferably less than about0.001 inches or 0.0008 inches or less. In the catheter axial direction,the length of the struts 440 is at least about 0.50 mm or 0.75 mm, andin one embodiment the length of the struts 440 and sliders 441 is about1 mm.

Referring to FIG. 8A, a modified distal tip 50 includes a helical thread52 extending from a distal tip 54 to a proximal end 56 and supported bya core wire 58. The axial length of the distal tip 50 is at least about2 mm or 5 mm or 10 mm and in some embodiments no more than about 30 mmor 20 mm measured along the core wire 58. The helical thread 52 wrapsaround the axis at least about 1 or 2 or 4 or more full revolutions, butin some embodiments no more than about 10 or 6 revolutions. In someembodiments the axial length along the threaded portion of the tip iswithin the range of from about 1 to about 8 revolutions.

The helical thread 52 on this implementation may have a constant pitchthroughout its length. The pitch may be within the range of from about10 to about 20 threads per inch, or about 5 to about 10 threads per inchdepending upon desired performance. Alternatively, the thread may havemultiple pitches designed to engage, transport and grasp thrombus withinthe catheter lumen. A distal pitch may be less than a proximal pitch.The pitch may vary continuously along the length of the thread, or maystep from a first, constant pitch in a proximal zone to a second,different pitch in a distal zone of the thread. The thread 52 maycomprise a continuous single helical flange, or may have a plurality ofdiscontinuities to produce a plurality of teeth or serrations, arrangedhelically around the core wire.

The side elevational profile or envelope scribed by the distal tip as itrotates may have a linear or nonlinear taper on one or both ends whichprovide varying diameter and thus clearance along its length from thegenerally cylindrical ID of the catheter lumen. The maximum outerdiameter 60 of the envelope (Max OD) is defined by the major diameter ofthe thread, and the tapers may be optimized for improved thrombusengagement and/or thrombus clearance as the helical thread element isrotated in the catheter.

Referring to FIG. 8A, the Max OD 60 in a first zone may be up to thediameter of a sliding fit within the catheter lumen, and may generallybe at least about 0.015 inches or 0.010 inches smaller than the catheterlumen ID. In some implementations, the Max OD of the tip may besignificantly less than the inside diameter of the catheter lumen toallow more space for the thrombus, but still create significant graspingforce via engagement of the helical threads with the thrombus. In oneimplementation, the maximum helical thread diameter is about 0.110inches and the catheter lumen ID is about 0.275 inches (24 F) (a 0.165inch gap between the helical threads and catheter wall.

In the illustrated embodiment, the side elevational view profile of thehelical thread OD tapers down in a proximal direction in a second zone,and tapers down in a distal direction in a third zone, such that the MaxOD occurs with the central 30% or 20% or 10% of the axial length betweendistal tip 54 and proximal end 56.

The radial depth of the threads from the core 58 (minor diameter) to theoutermost free edge 53 of the thread elements (major diameter) can bevaried by varying either the major diameter as described above, as wellas by varying the minor diameter (by varying the diameter of the core).The core may have a constant diameter throughout its length, or maytaper, typically smaller in the distal direction as seen in FIG. 8.

The profile of the tip 50 viewed along the axis of rotation may becircular, or may vary to create a non circular pattern around the axisof rotation as seen in FIG. 9. The tip as seen in an end elevationalview thus exhibits a major diameter 62 and a minor diameter 64. Theminor diameter may be no more than about 95% or 90% or 80% or 70% of themajor diameter, depending upon desired performance.

In certain applications, the Max OD of the tip is no more than about 35%or about 50% or about 60% of the ID of the catheter, to leave asubstantial tip bypass flow path. Since this implementation does nothave any centering structures, the tip will normally be pushed to oneside of the aspiration lumen. When a clot becomes lodged between the tipand the opposing wall of the catheter, manual rotation of the tip canengage the clot like a worm gear and either grasp the clot (e.g., bypinning it against the opposing catheter sidewall) for retraction orfacilitate freeing the blockage and aid in ingestion of the clot intothe catheter.

A variation of the distal tip 50 is illustrated in FIGS. 8B and 8C. Theillustrated tip 50 includes a distal advance segment 55 extendingbetween an atraumatic distal tip at 54 and a transition 57. Helicalthread 52 extends proximally from transition 57 to a proximal end 56 ofthe helical thread 52. A trailing segment 59 extends between theproximal end 56 of the thread and the proximal end of the tip. Thethread may be inclined in a proximal direction, to produce a proximallyfacing undercut and a distal surface that inclines radially outwardly ina proximal direction.

The axial length of the advance segment 55 may be at least about 1 cm or2 cm and in some implementations is within the range of from about 2 cmto about 4 cm. The axial length of the helical thread 52 along thelongitudinal axis is typically within the range of from about 1 cm toabout 5 cm and in certain implementations between about 2 cm and 3 cm.

The outside diameter of the advance segment 55 at distal tip 54 isgenerally less than about 0.024 inches, or less than about 0.020 inchesand, in one implementation, is about 0.018 inches. The maximum outsidediameter of the advance segment 55 and helical thread 52 may be withinthe range from about 0.020 to about 0.050 inches, and, in oneimplementation, is less than about 0.040 inches, such as about 0.035inches. The advance segment, helical thread and trailing segment of thetip 50 may be molded over the core wire 58 using any of a variety ofpolymers known in the catheter arts.

Referring to FIG. 8C, a first radiopaque marker 63 may be carried on thecore wire 58 beneath the advance segment 55. A second radiopaque marker65 may be carried on the core wire 58 within the trailing segment 59.Each radiopaque marker may comprise a coil of radiopaque wire such as aplatinum iridium alloy wire having a diameter about 0.002 inches, andwrapped around the core wire 58 and soldered to the core wire 58 toproduce an RO coil having an outside coil diameter of less than about0.020 inches, such as about 0.012 inches. The radiopaque markers mayalso function as an axial interference fit between the core wire 58 andthe molded advance segment 55 and trailing segment 59 to resist corewire pull out from the tip 50.

In one implementation, the maximum OD of the thread 52 exceeds themaximum OD of the advance segment 55 by at least about 15% or 25% or 30%or more of the OD of the advance segment 55, to facilitate crossing theclot with the advance segment 55 and engaging the clot with the thread.The thread pitch may be within the range of from about 0.75 to about0.30, or within the range of from about 0.10 and about 0.20, such asabout 0.14 inches.

Preferably, the maximum OD of the tip 50 is less than about 60% or 50%of the aspiration catheter ID, and may be within the range of from about35% to about 55% of the catheter ID. In certain implementations, themaximum OD of the tip 50 may be within the range of from about 0.044inches to about 0.050 inches within a catheter having an ID within therange from about 0.068 inches to about 0.073 inches.

For this configuration of the tip 50, the distal stop on the proximalend of the core wire 58 is configured to permit distal advance of thetip 50 such that the distal end 54 may be advanced at least about 2 to 3cm and preferably as much as 4 to 8 cm beyond the distal end of thecatheter. In one implementation, the distal stop limits distal advanceof the tip 50 so that the proximal end is within two or within one orthan 0.5 cm in either the distal or proximal direction from the distalend of the aspiration catheter.

Referring to FIG. 10, the helical tip element may be part of anover-the-wire structure which can be moved over a guide wire. Thisstructure allows the guide wire to be positioned and the helical tippedstructure can be inserted with a surrounding catheter, or independentlyinto a surrounding catheter which is already in place and over theguidewire. The helical tip structure can be rotated freely around theguide wire. The lumen 66 may be used for a guide wire or other devicesor fluids to communicate from proximal end of the torque member throughthe distal tip of the helical tip element.

FIG. 11 illustrates one embodiment of an over-the-wire helical tippedengagement wire 46 with a central lumen having guidewire 70 extendingtherethrough. Similar to other helical tip structures disclosed therein,this is intended to operate within a coaxial surrounding catheter as hasbeen previously discussed. As with implementations discussed elsewhereherein, engagement wire 46 includes an elongate flexible body configuredto transmit torque between a proximal hub or handle 70 and the distaltip 50. The body may comprise a torque coil construction as disclosedelsewhere herein, having two or more concentric coils typically wound ina reverse direction from the adjacent coil. The engagement wire 46optionally includes an axially extending longitudinal stabilizer 82.Preferably, the torque coil is enclosed within a polymeric jacket suchas a shrink wrap tube.

The helical tip may alternatively have a fixed guide wire 72 distaladvance segment extending from the distal end of the helical tip (SeeFIG. 12) or a polymeric distal extension to provide an atraumatic tip(See FIG. 8B). This fixed guide wire advance segment is typically easilybent when interacting with the patient's anatomy to avoid injuringtissue. The fixed guide wire advance segment may be between about 1 cmand about 10 cm but may be shorter or longer depending on theapplication.

In accordance with another aspect of the invention, a catheter dilatorsheath assembly is provided to enable easy, safe, and efficient trackingof a large diameter catheter or catheter system from insertion into alarge peripheral blood vessel and advanced to the target location ofinterest. The large diameter catheter, such as for aspiration or othermechanical means of removal of embolus or thrombus from large vessels,has a diameter within the range from about 8 F (0.105″) to about 24 F(0.315″).

Referring to FIGS. 6 and 13, one implementation of the catheter 60includes an elongate flexible tubular body 50, having a proximal end 52,a distal end 54 and a side wall 56 defining a central lumen 58.Referring to FIG. 14, an elongate flexible cannulated rail or dilator 61is shown extending over the guidewire 70 and occupying the space betweenthe guidewire 70 and the large inside diameter of the central lumen 58of the large diameter catheter 60 to provide support to the catheterand/or an atraumatic tip during delivery.

This catheter-cannulated rail-guidewire assembly is intended to easilytrack through anatomical challenges more easily than the catheter. Thecatheter-rail-guidewire assembly then acts as a first stage of thecatheter delivery system and enables the large diameter catheter orcatheter system to be inserted and independently advanced over thisfirst stage into a blood vessel (e.g. the femoral vein) percutaneouslyover a guidewire and advanced through potentially tortuous vasculatureto the remote target location of interest without requiring advancedskills or causing kinking of the catheter.

The cannulated rail 61 may comprise a soft flexible cylindrical bodyhaving a guidewire lumen with a diameter of no more than about 0.040″and an outside diameter no greater than about 0.025″ or about 0.010″smaller than the inner diameter of the large diameter catheter. Thus thewall thickness of the cannulated rail 61 is typically at least about0.010″ less than the radius of the large diameter catheter and in someimplementations at least about 0.120″ or more, depending upon the sizeof the annular space between the inside diameter of the catheter and theoutside diameter of the guidewire. Depending upon the ID of the accesscatheter, the rail 61 may have a wall thickness of at least about 0.05inches, at least about 0.075 inches, at least about 0.100 inches and insome implementations at least about 0.12 inches. The wall thickness ofthe rail may exceed the inside diameter of the guidewire lumen.

The cannulated rail 61 may have an elongated advance segment having atapered distal tip 62 that may project beyond the distal end 54 of thecatheter 60. The thick sidewall of the cannulated rail 61 may compriseone or more flexible polymers, and may have one or more embedded columnstrength enhancing features such as axially extending wires, metal orpolymeric woven or braided sleeve or a metal tube, depending upon thedesired pushability and tracking performance along the length of thedilator.

Optionally, the proximal segment of the rail or dilator which is notintended to extend out of the distal end of the catheter may be astructure which is not coaxial with the guidewire, but is instead acontrol wire which extends alongside the guidewire in the catheter andallows the distal tubular telescoping segment of the rail or dilator tobe retracted or extended. (analogous to rapid exchange catheters)without the entire length of the rail structure being over the wire.This allows removal or insertion of the rail or dilator over a shorterguidewire because of the shorter coaxial segment tracking over theguidewire. The distal tubular segment may have a length of no more thanabout 40 cm or 30 cm or less, carried by a proximally extending controlwire.

Catheter 60 may be provided with a proximal hub 120, having a port foraxially movably receiving the rail 61 therethrough. The hub 120 may beprovided with an engagement structure such as a first connector 122 forreleasably engaging a second complementary connector 124 on a hub 126 onthe proximal end of the rail 61. First connector 122 may comprise aninterference structure such as at least one radially moveable projection130, for releasably engaging a complementary engagement structure suchas a recess 132 (e.g., an annular ridge or groove) on the hub 126.Distal advance of the rail 61 into the catheter 60 causes the projection130 to snap fit into the recess 132, axially locking the catheter 60 andrail 61 together so that they may be manipulated as a unit.

The dilator is inserted through the hemostasis valve in the hub 120 of alarge bore (e.g., 24 F) catheter 60 and advanced through the catheteruntil the retention clip on the dilator hub 126 or catheter hub 120snaps into the complementary recess on the other hub. In this engagedconfiguration, the flexible distal end of the 24 F rail dilator 61 willextend at least about 5 cm or 10 cm, and in some implementations atleast about 15 cm or 20 cm beyond the distal end 54 of the 24 F catheter60. The rail dilator and 24 F catheter system are thereafter distallyadvanced over a previously placed guidewire and into the introducersheath.

The dilator and catheter combination of the present inventiondifferentiate over prior systems both because of the flexibility of adistal zone of the dilator and greater length of the dilator than thecorresponding catheter. Typically, a dilator is a uniform stiffness andlength-matched to its catheter, with only a short atraumatic tip of thedilator extending beyond the distal end of the catheter. The dilator ofthe present invention has a supportive proximal end and a flexibledistal end, with a total dilator length much longer than the catheter 60to enable, as an example, the following procedure.

In use, a guidewire 70 such as an 0.035″ guidewire is advanced underfluoroscopy using conventional techniques into a selected vessel. Thecannulated rail 61, optionally with the catheter 60 mounted thereon, isloaded over the proximal end of the guidewire 70 and advanced distallyover the wire until the distal end of the rail is in position at thetarget site.

The 24 F catheter 60 is thereafter unlocked from the rail 61 andadvanced over the rail 61 to the desired site, supported by the rail 61and guidewire 70 combination. Because the uncovered advance section ofthe rail has already traversed the challenging tortuosity through theheart, the catheter 61 now just slides over the advance section of therail for easy passage to the final target location. The supportiveproximal zone and flexible distal advance section of the rail enablesease of delivery through the most challenging anatomy in, for example, aPE procedure going from the vena cava through the tricuspid andpulmonary valves of the heart into the central pulmonary artery withoutconcern about damaging the tissue (atraumatic, flexible tip) or damagingthe dilator (high kink resistance due to flexible, high wall thickness“solid” dilator construction.

The cannulated rail 61, or the cannulated rail 61 and the guidewire 70combination, may thereafter be proximally withdrawn, leaving the largebore catheter 60 in position to direct a procedure catheter such as anyof the aspiration catheters disclosed elsewhere herein to the targetsite.

Referring to FIG. 15, the large diameter (LD) catheter 60 may in somesituations have a smaller diameter (SD) catheter though its centrallumen for the purposes of introducing an additional functionality (e.g.,clot grabber catheter 62, imaging catheter 10, or mechanicalthrombectomy tool 66) and/or telescoping the SD catheter to more distallocations in the anatomy. In order to enable delivery of the LD catheter60 and SD catheter as a single system, the SD catheter may have a coredilator 68 for support, and the gap between the outer diameter of the SDcatheter and inner diameter of the LD catheter 60 may be maintained orsupported by a second, tubular dilator 71. The tubular dilator 71 mayhave a shaped distal tip 72 for a smooth tapered transition from the SDcatheter 41 to the LD catheter 40. The distal end 34 of the core dilatormay be provided with a complementary taper to the distal taper of thethin wall SD dilator (FIG. 16) or may end at the distal end of the LDcatheter (FIG. 17).

The core dilator 68 inside the SD catheter 41 and tubular dilator 70between the two catheters may have an interlocking feature to create asingle (SD+LD) catheter+(core+tubular) dilator system. For example,complementary connectors may be provided on hubs on the proximal ends ofthe system components.

Referring to FIG. 17, the tip of the tubular dilator 70 may beconfigured to taper to the guidewire lumen 76, thus covering andextending distally beyond the small diameter catheter 41 if it is inplace. The tip of the tubular dilator 70 may be provided with alongitudinally extending slit 78, scored or perforated one or more timesto allow the tip to split longitudinally and be pulled back into thespace between the LD and SD catheters and fully expose the distal end ofthe small diameter catheter 41. See FIG. 18.

The single (SD+LD) catheter+(core+tubular) dilator system may bepre-assembled and detachably interlocked at the proximal hub. Additionaltubular dilators having a series of outside diameters and wallthicknesses may be provided such that the SD catheter may be used incombination with different diameter LD catheters. A LD catheter may beused with different SD catheters by providing tubular dilators havingthe same OD but a series of different inside diameters. The core+tubulardilators may simply be pulled proximally to withdraw both dilators as asingle system, or the tubular dilator may be configured with a tab orhandle at the proximal end and a slit, scoring, perforation or othermechanism so as to split, peel, or tear it along the longitudinal axisduring withdrawal to allow the tubular dilator to peel from the SDcatheter as it slides proximally out of the space between the LD and SDcatheters. (FIG. 18)

Any of the thrombectomy catheters disclosed herein may be provided witha surface configuration on the inside surface of the central lumen toaffect the behavior of clot drawn into the lumen. In general, thecatheter, with diameter within the range from about 8 F (0.105″) toabout 24 F (0.315″), includes an elongate flexible tubular body, havinga proximal end, a distal end and a side wall defining a central lumen.The access or evacuation catheters may also include a rotatable corewire or other apparatus that extends though the catheter lumen for thepurposes of engaging thrombus at the distal end of the catheter as hasbeen discussed.

The central lumen 90 is defined by an inside surface 100 of the tubularbody 104, which in some embodiments is a smooth cylindrical surface.However, referring to FIGS. 19A and 19B, the inner surface 100 of atleast a distal zone 102 of the tubular body 104 may be provided with asurface configuration to engage thrombus and limit unrestricted slidingof the thrombus along the inner surface 100. The distal zone 102 mayhave an axial length within the range of from about 0.5″ to about 12″ ormore, depending upon desired performance and/or manufacturing technique.

For example, referring to FIG. 19A, at least one or five or ten or moreaxially extending surface structures such as radially inwardly extendingridges 106 separated by grooves 108 may be provided to facilitateproximal ingestion of the thrombus and/or to engage thrombus and resistrotation of the thrombus within the lumen when the core wire or otherthrombus grabbing apparatus is rotated within the lumen.

The corrugation pattern may also increase the transport of the thrombusproximally by decreasing the surface area of contact between thethrombus and the inside surface of the tubular body. The spacingcircumferentially may be regular or irregular, and the crest and troughpattern, dimensions and distribution may be varied. Examples of troughcross sections include the illustrated rectangular, semicircular ortriangular, among others.

In one implementation illustrated in FIG. 19B, the surfacediscontinuity, i.e. grooves or ridges, may extend in a circumferential(e.g. helical) configuration having a constant or variable pitch alongthe length of the distal zone 102. The helical guide may spiral in afirst direction in order to oppose rotation of the core wire or otherapparatus in a second direction, or in the same direction to cooperatewith the rotation of the core wire in order to facilitate thrombusingestion proximally into the catheter. The grooves or ridges may have acurved profile or generally rectilinear, having generally flat orcylindrical side walls.

In another embodiment, the inner surface 100 of the distal zone 102 ofthe tubular body 104 may have a three-dimensional pattern that reducefriction of the thrombus moving proximally in the catheter and createresistance to the thrombus moving distally in the catheter after it hasbeen ingested into the catheter. This pattern may be regular throughoutor in the distal end of the tubular body, or irregular and decreasegradually and progressively in density, pattern, or geometry along thelength of the catheter or the distal section. This pattern may also beprovided in combination with lubricious coatings or surfaces.

The three-dimensional differential friction pattern may be defined by aregular or irregular pattern of protuberances 110 or depressions on theinner surface of the catheter, each of which presents an exposed face112 inclined radially inwardly in the proximal direction, with eachinclined exposed face 112 terminating proximally in a proximally facingengagement surface such as a dropoff edge 114, which may be curved in anaxial direction as shown in FIG. 21 to provide a ratchet or fish scaletype of configuration.

The scales may flex, hinge or pivot at the distal end, which will notimpact the proximal ingestion of the thrombus, but will createadditional resistance to the thrombus moving distally in the catheterafter it has been ingested into the catheter.

In alternative embodiments, the differential friction surface structureson the inner surface of the distal zone may be relatively shallow convexor concave “dimples” or other regular or irregular surfacediscontinuities that are generally triangular, oval, oblong arcs,serpentine shapes or a plurality of angled fibers that incline radiallyinwardly in a proximal direction.

Referring to FIG. 22, the lumen 116 of the tubular body may benon-cylindrical and instead be oval or other geometry lacking rotationalsymmetry and containing a minor axis which is less than a major axis dueto one or more longitudinal deformations of the lumen. Theselongitudinal deformations of at least the inner surface of the tubularbody serve as structures to increase the rotational resistance tothrombus or embolic matter in the lumen. These deformations may containtheir own lumens within the wall of the tubular body for pull wires of asteerable tip or to deliver fluids or to measure pressure or to transmita vacuum or other functions.

The distal end 118 of the tubular body may be angled such that thedistal face of the catheter resides on a plane or a curve with an end toend secant that crosses the longitudinal axis of the tubular body at anangle within the range from about 30 degrees to about 60 degrees. Thedistal face of the angled tip may be non-planar and may include one ortwo or more inflection points or curves. This angled tip may improvecatheter navigation and thrombus ingestion by providing more surfacearea for engagement between the catheter and the thrombus. (see, e.g.,FIG. 31D and associated description in US publication No. 2020/0001046A1 to Yang, et al., which is hereby incorporated in its entirety hereinby reference.)

The opening at the distal end of the tubular body may be expandable froma first inside diameter for transluminal navigation to a second, largerinside diameter providing a funnel like tip with an enlarged distalopening to facilitate aspiration of thrombus into the lumen. Thediameter at the distal opening of the fully open funnel exceeds thediameter of the cylindrical distal end of the tubular body by at leastabout 5% or 10% or more. (see FIGS. 4A-41 and associated description inU.S. Pat. No. 10,441,745 to Yang, et al., which is hereby incorporatedin its entirety herein by reference.)

The distal end of the catheter may have an increasing inner diameterwhile maintaining a constant outer diameter, representing a tapereddistal wall, or the inner and outer diameters may both increase,representing a conical funnel like tip.

The funnel tip is may be made of a material that is rigid enough tomaintain structural integrity under aspiration and flexible enough thatit may deform to accommodate and enable thrombus across a range of size,shape, and maturity to be aspirated into the catheter lumen.

The funnel tip may telescope out of the thrombectomy catheter. A hollowcylindrical structure at the end of a long, flexible hypo tube or at theend of two or more stiff wires may be advanced through the catheter, andwhen the hollow cylindrical structure extends beyond the distal cathetertip and its associated circumferential constraint, the structure expandsinto a conical funnel shape. Additional details of these features may befound in U.S. Pat. No. 10,441,745 to Yang, et al., previouslyincorporated in its entirety herein by reference.)

The thrombectomy catheter with inner lumen features to enhance theextraction of thrombus and/or distal end features may enable easier,more efficient removal of a broad spectrum of thrombus size, shapes, andmaturity from vascular conduits including the pulmonary arteries,resulting in shorter procedure times and a lower total volume of bloodloss. This is achieved by promoting proximal movement of the thrombuswhile creating resistance to the thrombus moving distally in thecatheter after it has been ingested into the distal catheter.

The foregoing inventions and improvements will enable the engagement andcapture of a very wide range of thrombus, from acute to mature innature, thus enabling the extraction of the thrombus from the bloodvessel in which it may be impeding blood flow. Additionally, theconfigurations described above enhance safety by reducing the risk ofvascular tissue injury due to mechanical engagement of the helical tipelement and/or catheter tip with the vessel wall.

In the foregoing description, similar features in different drawings aresometimes identified by slightly differing terminology. This is notintended to imply differences that do not exist. Slightly differentfeatures are illustrated in different drawings, and those of skill inthe art will recognize that any of the features disclosed here in can bere-combined with any of the catheters or other structures disclosed herein.

What is claimed is:
 1. A system for accessing a pulmonary artery,comprising: an elongate, flexible tubular access catheter, having aproximal end, a distal end, and an access catheter hub on the proximalend; an elongate, flexible rail, having a proximal end, a distal advancesegment, and a rail hub on the proximal end; wherein the distal advancesegment of the rail extends at least 10 cm beyond the distal end of theaccess catheter when the access catheter hub is adjacent the rail hub.2. A system as in claim 1, further comprising an engagement structure onthe access catheter hub, configured to releasably engage a complementaryengagement structure on the rail hub.
 3. A system as in claim 1, whereinthe distal advance segment of the rail extends at least about 15 cmbeyond the distal end of the access catheter when the access catheterhub is adjacent the rail hub.
 4. A system as in claim 1, wherein therail increases in flexibility in a distal direction.
 5. A system as inclaim 1, wherein the rail comprises a guidewire lumen.
 6. A system as inclaim 5, wherein the guidewire lumen can accommodate a guidewire havinga diameter of no greater than about 0.035″, the catheter is at leastabout 20 French, and the rail has an outside diameter that is no morethan about 0.025″ smaller than the inside diameter of the accesscatheter.
 7. A system as in claim 1, wherein the access catheter hubcomprises a hemostasis valve.
 8. A system as in claim 2, wherein theaccess catheter hub comprises a projection configured to snap fit into arecess on the rail hub.
 9. A system as in claim 5, wherein the wallthickness of the rail is at least about 0.05 inches.
 10. A system as inclaim 5, wherein the wall thickness of the rail is at least about 0.10inches.
 11. A system as in claim 1, wherein the access catheter is atleast about 8 French.
 12. A system as in claim 1, wherein the accesscatheter is at least about 20 French.
 13. A system as in claim 1,further comprising a thrombus evacuation catheter configured to extendthrough the access catheter.
 14. A system as in claim 13, furthercomprising a thrombus engagement tool configured to extend through thethrombus evacuation catheter.
 15. A system as in claim 14, wherein thethrombus engagement tool comprises an elongate flexible body having athrombus engagement tip with a helical thread.
 16. A system as in claim15, wherein the thread extends from about two to about 10 revolutionsaround the elongate flexible body.
 17. A system as in claim 16, whereinthe thread has a maximum diameter that is no more than about 60% of aninside diameter of an adjacent portion of the thrombus evacuationcatheter.
 18. A system as in claim 15, further comprising a handle onthe proximal end of the thrombus engagement tool configured to permitmanual rotation of the thrombus engagement tool.
 19. A system as inclaim 4, wherein the rail comprises a proximal segment separated fromthe distal advance segment by a transition.
 20. A system as in claim 19,wherein the distal advance segment has a greater flexibility than theproximal segment.